can you rotate 5d video
 

I shot some footage off a train but held the camera vertically now on playback it looks strange as i thought there would be a way in the media player to rotate the picture but seems only photos can be rotated ,am i wrong

You can easily rotate it in your NLE, but not a media player.

I shoot fashion video in portrait orientation all the time. Premiere Pro has no problem rotating it using the built-in motion filter. Of course I don't actually use the filter to rotate it during the video. I just leave it at +- 90 degrees. There doesn't appear to be any quality degradation.

On a Mac (and maybe Windows too?) you can rotate with Quicktime Player Pro. Open the file in QT, and then select Movie Properties, then click on video track and then visual settings. There you'll see arrows for rotating the image.